.java

public class RespondToJavaService implements BasicLibraryService  {

  @Override
  public boolean basicLoad(Ruby ruby) throws IOException {
    ruby.defineModule("Foo").defineClassUnder("Bar", ruby.getObject(), new ObjectAllocator() {
      @Override
      public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
        return new RespondTo(runtime, klazz);
      }
    }).defineAnnotatedMethods(RespondTo.class);
    return true;
  }

  @JRubyClass(name = "RespondTo")
  public static class RespondTo extends RubyObject {

    public RespondTo(Ruby runtime, RubyClass klazz) {
      super(runtime, klazz);
    }

    @JRubyMethod(name = "respond_to?", required = 1, optional = 1)
    public static IRubyObject respondTo(ThreadContext context, IRubyObject self, IRubyObject[] args) {
      System.err.println("Custom repond_to? got called!");
      
      // below line requires `frame = true` to set up a call frame for `super`
      // return Helpers.invokeSuper(context, this, metaClass, "respond_to?", args, Block.NULL_BLOCK);
      
      // instead you can just call the default impl directly
      return self.respondTo(context, args);
    }
  }
}